Desmearing and etchback are known technologies wherein both wet chemical and plasma techniques are practiced in the board fabrication industry.
U.S. Pat. No. 4,328,081 describes a particular chamber configuration for accomplishing plasma desmearing. The preferred plasma for accomplishing the desmearing in this patent is recited at column 2, line 46 as being oxygen and carbon tetrafluoride.
U.S. Pat. No. 4,425,210 discloses a multiple electrode set configuration for plasma desmearing of printed circuit boards or multiple layered printed wire boards. Again, at column 2, line 46, the selected plasma is comprised of oxygen and carbon tetrafluoride.
U.S. Pat. No. 4,496,420 discloses a method for desmearing multilayered laminated printed circuit boards using an apertured plate in conjunction with plasma desmearing. Appropriate board compositions includes acrylic, polyimide, Kapton, Kevlar and epoxy. All of these materials are known to smear during processing, most notably in drilling holes through printed circuit boards for subsequent electrical contact or assembly.
U.S. Pat. No. 30,505 discloses a process for plasma etching of a solid material with a binary mixture comprising essentially oxygen and a halocarbon wherein at least one carbon atom in said molecule is linked to a predominance of fluorine atoms.
U.S. Pat. No. 3,930,913 discloses a method for removing a patterned layer of organic material from a metallic sublayer wherein a plasma comprising a mixture of oxygen and nitrogen is used to remove the organic material. Both the oxygen and the nitrogen are present in their uncombined elemental form.
U.S. Pat. No. 4,310,380 discloses a dry plasma etch process for silicon surfaces using a gas composition wherein the compounds of the gaseous composition are selected from the group consisting of chlorine trifluoride, nitrogen trifluoride, bromine trifluoride and iodine trifluoride.
U.S. Pat. No. 4,374,698 describes an etch process for differential etching of silicon nitride from silicon dioxide using the combination of carbon tetrafluoride and a halofluorocarbon. The gas etchant may include oxygen or nitrous oxide.
U.S. Pat. No. 4,473,437 discloses a process for etching organic material layers using a dry plasma of oxygen and nitrogen-containing mixtures.
U.S. Pat. No. 4,522,681 discloses a method for etching holes in silicon dioxide wherein a dry plasma etch gas of argon, nitrogen trifluoride and oxygen may be used. Polymeric photoresist materials such as polymethyl methacrylate, ethyl methacrylate, methyl isopropyl ketone as well as copolymers thereof with metacrylic acid may be used. This class of photoresist materials was required, versus standard novel AC photoresists, to successfully practice the invention.
U.S. Pat. No. 4,568,410 discloses a dry plasma etch process for etching silicon nitride using nitrogen trifluoride and oxygen. Good results for etching silicon nitride were found with relative percentages of the nitrogen trifluoride to oxygen recited at column 5, line 65 to be 10-20 SCCM of NF.sub.3 in comparison to 20-35 SCCM for oxygen. The gases are also discloses as capable of etching common resists.